All responsible server admins have them defederated. Hate speech and genocide denial, that is almost certainly against the law in Canada, Germany, and other places. We defederated lemmygrad for the same reason.
Or they live in a country where genocide denial is legal. I live in Canada and my server is in Canada. I’m not willing to take the risk so my users can interact with assholes.
In your instance' case, db0 has said IIRC that the Anarchists on Hexbear, while not aligning 100% with them, are generally good and worth being federated with.
Instance block is not as effective as defederation, even on an individual level. I have received replies and messages from accounts on blocked instances; nothing gets through defederation.
I got a bit of harassment from hexbear users when I started using Lemmy, haven't in a while now though, I have blocked around 30 of them and instance block
I don't want it to. I think instance admins should be defederating from spambot farms, but not much more than that; if there's a chance some of its users want to read it, they should allow its users to.
That is, I want my instance admins to engage in moderation, but not censorship. I think defederating from extremist politics (whether far-left or far-right) is usually censorship, not moderation.